56 lines
1.9 KiB
Diff
56 lines
1.9 KiB
Diff
From 3fbb44532ce16ee6c0e7a45e89952e5f7d339045 Mon Sep 17 00:00:00 2001
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From: Frank Rowand <frank.rowand@am.sony.com>
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Date: Wed, 16 May 2012 18:09:36 -0700
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Subject: [PATCH 277/290] fix printk flush of messages
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Updates console-make-rt-friendly.patch
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#ifdef CONFIG_PREEMPT_RT_FULL, printk() output is never flushed by
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printk() because:
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# some liberties taken in this pseudo-code to make it easier to follow
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printk()
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vprintk()
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raw_spin_lock(&logbuf_lock)
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# increment preempt_count():
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preempt_disable()
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result = console_trylock_for_printk()
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retval = 0
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# lock will always be false, because preempt_count() will be >= 1
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lock = ... && !preempt_count()
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if (lock)
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retval = 1
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return retval
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# result will always be false since lock will always be false
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if (result)
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console_unlock()
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# this is where the printk() output would be flushed
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On system boot some printk() output is flushed because register_console()
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and tty_open() call console_unlock().
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This change also fixes the problem that was previously fixed by
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preempt-rt-allow-immediate-magic-sysrq-output-for-preempt_rt_full.patch
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Signed-off-by: Frank Rowand <frank.rowand@am.sony.com>
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Cc: Frank <Frank_Rowand@sonyusa.com>
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Link: http://lkml.kernel.org/r/4FB44FD0.4090800@am.sony.com
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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kernel/printk.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/kernel/printk.c b/kernel/printk.c
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index 9eabbbb..66e83e5 100644
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--- a/kernel/printk.c
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+++ b/kernel/printk.c
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@@ -836,7 +836,7 @@ static int console_trylock_for_printk(unsigned int cpu, unsigned long flags)
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int retval = 0, wake = 0;
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#ifdef CONFIG_PREEMPT_RT_FULL
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int lock = (!early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
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- !preempt_count()) || sysrq_in_progress;
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+ (preempt_count() <= 1)) || sysrq_in_progress;
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#else
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int lock = 1;
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#endif
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